The purpose of this study is to determine whether neoplastic cells confer significant metabolic advantage over normal cells. We are interested in whether or not amino acid transport systems of normal cells change during maturation and whether functional properties of neoplastic cells differ from those of normal cells during the maturation process. We have initiated investigations of the transport of amino acids by both normal and neoplastic cells of the erythroid, myeloid and lymphoid series. During this project period work was concentrated on determining the transport properties of spleen derived lymphocytes and a comparison of these to those of the thymus derived lymphocytes. In our studies thymocytes show sodium-dependent transport of alpha-aminoisobutyric acid (AIB) and methylated AIB more than twice that seen in splenic lymphocytes. On the other hand, the sodium dependent steady state distribution ratio of alanine is about the same in both cell types. The sodium dependent steady state distribution ratio for AIB and methylated AIB in spleen lymphocytes is about equal to the sodium dependent steady state distribution ratio we found in erythroblastic leukemic cells. Our studies indicate that lymphocytes derived from the spleen and thymus transport amino acids by distinctly different systems. Thymic lymphocytes transport amino acids by both the sodium dependent "A" and "ASC" system but splenic lymphocytes only transport amino acids by the "ASC" system. The steady state distribution ratio for alanine is about the same in both thymic and splenic lymphocytes. We feel that the differences in amino acid transport between thymic and splenic lymphocytes clearly indicate that the two lymphocytes are functionally different and that the "T" lymphocytes in the spleen are functionally different from the "T" lymphocytes from the thymus gland.